2 THE AUDUBON ~BU DE hii 
the morning and 30 minutes to one and one-half hours after 4:30 o’clock 
in the evenings. 
The territory covered in Evanston is more favorable for migrating 
warblers than one would expect in a residential neighborhood. Most of 
the backyards are large with a rather heavy growth of shrubbery, and I 
regularly visited three vacant lots, two of which were covered with a dense 
thicket for most of the ten-year period, and one of them was in a secluded 
area on the lake. There is also a pool in Calvary Cemetery around which 
I spent considerable time. 
Some indication of the possibilities of this general section may be gained 
from the fact that I have recorded three yellow-breasted chats in the vacant 
lots, another one and a woodcock in a backyard 100 yards from my home, 
two Henslow’s sparrows in a yard back of our apartment and a lark 
sparrow only two blocks away from my home. 
In working up these records I was reminded of a lecture Dr. Oberholser 
gave to the Chicago Ornithological Society. He impressed upon us the fact 
that even the most experienced ornithologist has little conception of the 
number of birds seen at a given time unless he has actually counted and 
recorded them. Obviously, it is even more difficult for an amateur to make 
estimates in field work, and if I had not made notes and recorded them 
with considerable care, I would not believe some of the results. If I did 
not have a definite record, I would never believe that there was actually 
one year out of the ten that I did not see a black-throated green warbler; 
I would not believe that I saw an average of less than eight bay-breasted 
warblers per year, nor that four species of warblers comprised well over 
half of all warblers seen. 
I now regret that I did not record various data that would have added 
materially to the information accumulated, such as more exact notes on the 
weather, and a sample count at least once or twice each year of the 
proportion of identifications to the total numbers seen in a day. 
A comparison of the average arrival dates in table 1, with those shown 
in “Birds of the Chicago Region” published by The Chicago Academy of 
Sciences, discloses that, in most instances, my dates are almost a week later. © 
I found that there is not so much a definite peak in arrival dates, but 
rather a plateau. That is, the maximum number of each species seen 
extends over a period of several days. Some seasons the peak of abundance 
is limited to a single day, but over a period of years the maximum is of 
several days duration. 
In table 1 under the heading “maximum” I have shown the average 
range of dates for this sustained period of abundance. Whether or not it 
can be assumed that all were new arrivals or that a substantial number 
of those recorded during this period were present for several days, raises 
an interesting question. As a general rule though, it is known that 
migrants increase their rate of travel as they approach their nesting 
grounds, and in most instances warblers have covered the major portion 
of their northward journey when they reach our section. Weather condi- 
tions are also a factor to consider. However, I believe it is reasonable to 
